The long-range objective of this research is two-fold, (1) to quantify a theory fo phonation, and (2) to evaluate nonintrusive techniques that may have potential for studying phonatory control and diagnosing voice disorders. A series of empirical and theoretical studies, aimed at improved understanding of human phonation processes at the acoustic, aerodynamic, and biomechanical levels, is proposed. The first phase considers material properties of vocal fold tissue and aerodynamic properties of glottal constrictions in isolated, non-vibratory states. In vitro force-elongation measurements of vocal fold tissue and pressure-flow measurements in static laryngeal airway models provide first-order approximations to viscoelastic constants and glottal air resistance. The second phase embodies these first order approximations in a computer simulation model. Complex interactions between tissue movement and air movement are studied under self-oscillating conditions, and refinement of biomechanical properties in accomplished by comparing simulated model output with controlled measurements on excised larynxes. This includes a description of glottographic waveforms, which are parameterized for quantitative comparison between measurement and simulation. The third phase extends some of the biomechanic measurement techniques to the in vivo state in animals, where changes in the viscoelastic properties are studied as a function of active muscle control. In the applications of our phonatory theory, several broad questions that have linguistic, phoniatric, and pedagogical significance will be answered. There are (1) What control strategies at the muscular and configurational level within the larynx are used to change fundamental frequency, intensity, and register, (2) Which of the currently available nonintrusive (glottographic) techniques yields the most information about such muscular and configurational adjustments, and (3) What biomechanic and aerodynamic factors are involved in vocal fatigue and vocal pathology? An analysis package GLIMPES (Glottal Imaging by Processing External Signals) is under development for applications in clinics and voice laboratories.